00:01
Alright, according to beoza bart law, something like that, anyway, you have a wire with a current uniformly through it.
00:11
The radius of the wire is 40 but we are looking for the magnetic field only 20 centimeters.
00:20
I didn't convert centimeters away from the center.
00:29
So we have the magnetic field is equal to mu zero, which is the permittivity of free space, times the current over the circumference of the wire, 2 pi r, 2 pi capital r, so that's the circumference of the wire and then you take the ratio of where you want the magnetic field over the length of the whole thing.
01:11
I have to recalculate this due to the fact that i didn't take care of the centimeters.
01:18
I'm sure i should have had to do that.
01:20
R again, capital r is the 40, so we've got, let's see, 4 pi times 10 to the negative 7 times 8 times, let's see, 20 centimeters is actually 0 .2, so i have the same answer...